Method of forming a nonaqueous stable emulsion of rubber in polymerizable monomer, and the polymerization process and thermoplastic copolymer produced thereby

ABSTRACT

A process for the production of a nonaqueous stable emulsion feedstock comprising a rubber, a block copolymer having at least one component miscible with the rubber and at least one component miscible with the monomer, and at least two unsaturated organic monomers capable of free radical polymerization is disclosed. At least one of the monomers must be miscible with the rubber and the mixture of the monomers is substantially a nonsolvent for the rubber. The block copolymer maintains the rubber or rubber-rich particles in emulsified form within the mixture of monomers. In general, the process comprises (1) mixing the rubber, block copolymer and at least a portion of the rubber miscible monomers to form a first nonaqueous solution, (2) mixing the remaining monomers and the remaining portion of the rubber miscible monomers to form a second solution, and (3) combining the two solutions to form the nonaqueous stable emulsion feedstock. A process for polymerizing this feedback material and the polymerization product produced thereby is also disclosed.

This is a divisional of co-pending application Ser. No. 741,913 filedJune 6, 1985, now U.S. Pat. No. 4,698,389, which is a divisional of Ser.No. 705,266, filed Feb. 25, 1985, now U.S. Pat. 4,552,921, issued Nov.12, 1985.

BACKGROUND OF THE INVENTION

The present invention is directed to a novel process for fabricating anonaqueous emulsion feedstock for use in the preparation ofrubber-modified thermoplastic copolymers (two or more monomercomponents), a process for the preparation of rubber-modifiedthermoplastic copolymers and the new and improved rubber-modifiedcopolymers produced by this method. In particular, the polymerizationprocess of the present invention is characterized by the use of a singlenonaqueous stable rubber-containing emulsion feedstock comprising (1) amixture of free radical polymerizable unsaturated organic monomers whichmixture is substantially a nonsolvent for the rubber, (2) a rubber and(3) a block copolymer. The rubber-modified thermoplastic material of thepresent invention comprise the polymerization product of the nonaqueousemulsion feedstock. In particular the rubber-modified copolymers of thepresent invention may comprise the polymerization product of amonoalkenyl aromatic monomer, a C₁ to C₂ alkyl methacrylate and/oracrylonitrile, an unsaturated dicarboxylic anhydride, rubber and a blockcopolymer. A rubber-modified thermoplastic copolymer of the presentinvention comprising a monoalkenyl aromatic monomer, a C₁ to C₃ alkylmethacrylate, unsaturated dicarboxylic anhydride, rubber, and blockcopolymer is characterized by improved heat distortion temperature,transparency and impact strength.

Generally, rubber-modified copolymer compositions have been prepared byvarious procedures such as bulk inversion polymerization, aqueousemulsion polymerization, or solution polymerization. In particular,rubber modified terpolymers such as styrene/maleic anhydride/alkylmethacrylate have been made by solution polymerization as evidenced byU.S. Pat. No. 4,341,695.

Each of above-mentioned polymerization procedures has severelimitations. For example, aqueous emulsion polymerization or solutionpolymerization although enabling suitable rubber dispersion have theobvious disadvantage that the water or solvent which is present duringthe processing must be removed resulting in a severe economicdisadvantage.

Bulk inversion polymerization usually results in a matte finish polymerdue to the large (>1 micron) nonuniform particle size of the rubberformed. Furthermore, the process cannot be employed in conventionalreactors where the monomer mixture is a nonsolvent for the rubberycomponent. Bulk polymerization which employs an extruder as thepolymerization vessel overcomes some of these feedstock miscibilityproblems as well as alleviating some of the problems associated withaqueous emulsion or solution polymerization. In particular, reactorextruders of the twin screw design (see U.S. Pat. No. 4,463,137) providesufficient shearing action during polymerization of the monomers thatthe resulting rubber-modified copolymer has smaller size rubberparticles dispersed therein. However, there are some problems associatedwith reactor extruder polymerization. For example, the two feed solutiondescribed in U.S. Pat. No. 4,463,137 has potential pumping problemsassociated with the extremely high viscosity differential between thetwo feeds making it difficult to control the feed ratios. In addition,the dispersion of the intractable rubber rich phase in a desirablemanner in the polymerized product is particularly difficult to achievedue to the rapid rates advantageously used in the reactor-extruderpolymerization process. That is, there is not enough time for uniformdispersion of the rubber particles resulting in poor rubber phasedispersion in the finished products.

The present invention is directed to a procedure which alleviates theproblems associated with the above-identified procedures and the novelpolymerization produced by this procedure. The present inventionprovides a means for preparing a single feed mixture having a desiredlow viscosity and predetermined rubber particle size. This single feedmixture results in an evenly dispersed rubber phase within the bulkpolymerization product. The resulting rubber-modified polymerizationproduct of the present invention possesses unexpectedly superiorphysical characteristics compared to the rubber-modified polymerizationproducts known in the art.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process for thepreparation of a nonaqueous, stable emulsion comprising rubber orrubber-rich particles dispersed in a mixture of monomers.

It is another object of the present invention to provide a new andimproved process for the production of rubber-modified thermoplasticcopolymer.

It is a further object of the present invention to provide a process forthe production of a rubber-modified thermoplastic copolymer from asingle nonaqueous emulsion feedstock.

It is still another object of the present invention to provide a processfor fabricating a rubber containing nonaqueous emulsion feedstock havingimproved stability to coagulation.

It is a still further object of the present invention to provide aprocess for the production of a rubber-modified copolymer from a singlenonaqueous feedstock substantially free of inert organic solvent.

It is still another object of the present invention to provide a noveltransparent rubber-modified thermoplastic copolymer.

It is a further object of the present invention to provide a novelrubber-modified thermoplastic copolymer having improved heat distortiontemperatures and impact strength.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description that follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

To achieve the foregoing and other objects and in accordance with thepurpose of the present invention as embodied and broadly describedherein, the method of fabricating the rubber-containing nonaqueousstable emulsion feedstock of the present invention comprises combining(1) at least two miscible organic monomers at least one of which is asolvent for the rubber, (2) a block copolymer having at least onecomponent miscible with at least one of the monomers and at least onecomponent miscible with the rubber and (3) a rubber. The mixture ofmonomers is substantially a nonsolvent for the rubber; and the rubber isheld in emulsified form within the monomer mixture by the blockcopolymer. The procedure for combining the monomers, rubber, and blockcopolymer comprises (1) mixing at least a portion of one of the rubbermiscible (soluble) monomers, the rubber and the block copolymer to forma first nonaqueous solution, (2) mixing the remaining portion of therubber miscible monomers, and the remaining monomers to form anonaqueous second solution and (3) combining the first and secondsolutions to form a nonaqueous, stable emulsion comprising rubber orrubber-rich particles dispersed in the mixture of monomers.

Optionally, a portion of the remaining monomers (i.e. rubber-insolublemonomers) may be included in the first solution. However, it cannot bepresent in an amount which will cause the rubber to precipitate in thefirst solution.

In a preferred embodiment of the present invention, the size of therubber or rubber-rich particles is between 0.1 to 10 microns.

In another preferred embodiment of the process of forming the nonaqueousfeedstock of the present invention, the process includes forming thenonaqueous feedstock substantially free of any inert organic solvent(e.g. less than 5 weight %). The term inert organic solvent is definedfor purposes of this application as an organic solvent materialincapable of any type polymerization such as methyl ethyl ketone. Mostpreferably, the nonaqueous emulsion is completely free of inert organicsolvent.

In still another preferred embodiment of the present invention themonomers are selected to include unsaturated organic monomers capable offree radical polymerization.

In a further preferred embodiment of the process of forming thenonaqueous feedstock of the present invention the suitable classes offree radical polymerizable unsaturated organic monomers includeacrylates, acrylonitrile or its substituted homologs, acrylic acid oracrylic ester and its substituted homologs, acylamides, unsaturateddicarboxylic anhydrides, vinyl esters and monoalkenyl aromatic monomers.

In a still further preferred embodiment of the process of forming thenonaqueous feedstock of the present invention the free radicalpolymerizable monomers are selected to include C₁ to C₃ alkyl esters ofmethylacrylic acid, acrylonitrile or methacrylonitrile, unsaturateddicarboxylic anhydrides and monoalkenyl aromatic monomers.

The monoalkenyl aromatic monomer is preferably styrene but styrenederivatives such as alpha-methylstyrene, chlorostyrene,2,4-dichlorostyrene, p-methylstyrene and 2-chloro-4-methylstyrene may besubstituted for styrene in whole or part if desired. Most preferably,the monoalkenyl aromatic monomer is present in the range of 5 to 60parts by weight.

The unsaturated dicarboxylic acid anhydride is most preferably maleicanhydride though any of the homologs of maleic anhydride such asitaconic, citraconic, aconitic anhydrides can also be used.

The C₁ to C₃ alkyl ester of methylacrylic acid can be methylmethacrylate, ethyl methacrylate or propyl methacrylate. The preferredcopolymerizable monomer is methyl methacrylate.

The rubber component of the polymeric composition can be selected from awide range of alternatives including butadiene polymers and copolymers,styrene-butadiene rubber, ethylene/propylene rubber (EPR),ethylene/propylene/diene rubber (EPDM) and nitrile rubbers.

Preferably the block copolymer may comprise styrene/ethylene-butyleneblock copolymer when the rubber is EPDM or EPR or styrene/butadieneblock copolymer when the rubber is polybutadiene. Most preferably, thestyrene content of the block copolymer is at least about 25 weightpercent.

A further preferred embodiment of fabricating the stable nonaqueousemulsion of the present invention comprises (1) mixing a monoalkenylaromatic monomer, a rubber and a block copolymer having at least onecomponent miscible with the monomers and at least one component misciblewith the rubber and at least a portion of the C₁ to C₃ alkylmethacrylate in a first container to form a nonaqueous first solution,(2) mixing the remaining portion of the C₁ to C₃ alkyl methacrylate andan unsaturated dicarboxylic anhydride in a second container to form anonaqueous second solution, and (3) combining the first and secondsolutions to form the nonaqueous stable emulsion feedstock of thepresent invention.

In a further preferred embodiment of the present invention the amount ofmonoalkenyl aromatic monomer present in the solution is in the range ofabout 5 to 60 parts by weight. Most preferably, the monoalkenyl aromaticis styrene present in the range of 15 to 50 parts by weight.

In a still further preferred embodiment of the present invention,acrylonitrile may be substituted in part for the C₁ to C₃ alkylmethacrylate in the nonrubber containing solution.

In another preferred embodiment of the present invention, theunsaturated dicarboxylic anhydride is present in the range of about 5 to30 parts by weight and the C₁ to C₃ alkyl methacrylate and acrylonitrileare present in about 25 to 80 parts by weight. Most preferably, theunsaturated dicarboxylic anhydride is present in the range of 10 to 25parts by weight and the alkyl methacrylate and acrylonitrile are presentin the range of 30 to 70 parts by weight.

In still another preferred embodiment of the present invention therubber and block copolymer are present in about 5 to 30 parts by weight,most preferably 10 to 20 parts by weight.

In another aspect of the present invention the process of producing arubber-modified thermoplastic copolymer comprises placing the nonaqueousstable emulsion feedstock of the present invention in a polymerizationapparatus, heating the emulsion, optionally, in the presence of aninitiator, to polymerize the feedstock producing a rubber-modifiedthermoplastic polymer having an extremely uniform dispersion of rubberparticles throughout the polymeric matrix.

In a preferred embodiment of this aspect of the present invention, theinitiator is selected to include an organic peroxide initiator such asbenzoyl peroxide or dicumyl peroxide.

In a further preferred embodiment of this aspect of the presentinvention, the nonaqueous stable emulsion is fed to a reactor extruderand heated to an elevated temperature for a time sufficient topolymerize the emulsion. Typically, the emulsion is heated to atemperature in the range of about 120°-200° C. for about 2-20 minutes,optionally, in the presence of an initiator, and polymerized to producea rubber-modified thermoplastic polymer.

It is still another aspect of the present invention to provide a novelrubber-modified transparent thermoplastic terpolymer comprising styrene(Sty), methylmethacrylate (MMA), maleic anhydride (MAH), rubber and ablock copolymer having one component miscible with the monomers and asecond component miscible with the rubber.

In a preferred embodiment of this aspect of the present inventionstyrene is present in the range of about 5 to 30 parts by weight, maleicanhydride is present in the range of about 5 to 30 parts by weight,rubber and block copolymer are present in the range of about 5 to 25parts by weight, most preferably 10 to 20 parts by weight, and themethylmethacrylate is present in the range of about 50 to about 80 partsby weight.

In a further preferred embodiment of this aspect of the presentinvention the maleic anhydride (MAH) level was no greater then 30 partsby weight. Most preferably the MAH was present in the range of 15-30parts by weight.

It is still another aspect of the present invention to provide a novelrubber-modified thermoplastic copolymer comprising styrene, maleicanhydride, acrylonitrile, rubber and a block copolymer having at leastone component miscible with the monomers and at least one componentmiscible with the rubber.

In a preferred embodiment of this aspect of the present invention theacrylonitrile is present in the range of 10 to 50 parts by weight (pbw).Most preferably, the acrylonitrile is present in the range of about15-25 pbw.

In another preferred embodiment of the present invention the styrene ispresent in the range of 40 to 60 pbw, most preferably, 45 to 55 pbw.

In still another preferred embodiment of the present invention themaleic anhydride is present in the range of about 5 to 30 pbw. Mostpreferably, maleic anhydride is present in the range of about 15 to 25pbw.

The process of the present invention and the product produced provideseveral distinct advantages over the prior procedures and products. Forexample, the process of the present invention provides a procedure forfabricating a nonaqueous feedstock substantially free of any inertorganic solvent. In addition, the feedstock emulsion is quite stable tocoagulation and possesses a long shelf life thereby substantiallyeliminating any concerns regarding coagulation during temporaryproduction shutdown. Moreover, compared with conventional 15-25% solidsrubber solutions, the emulsion feedstock of the present inventionpossesses a relatively low viscosity and, furthermore, a uniformdispersion of rubber or rubber-rich particles in the monomer solution.The fact that this good dispersion in the feed solution remainsessentially unchanged on subsequent polymerization makes the single feedsystem particularly suitable for fast kinetic polymerization systems. Inaddition, the single feed emulsion of the present invention provides (1)a means of increasing the rubber content without causing high viscosityproblems and (2) a means to change the monomeric composition of theemulsion after formation without disturbing the stability of theemulsion.

Finally, due to the better rubber dispersion control, the productsproduced by the present invention have better gloss while maintainingother properties such as good impact strength and high heat distortiontemperature. In particular, the rubber modified thermoplastic copolymersof the present invention have exhibited improved heat distortiontemperature over similar rubber modified styrene, methylmethacrylatecopolymers and significantly improved impact strength overrubber-modified styrene (Sty), methylmethacrylate (MMA), maleicanhydride (MAH) terpolymers. For example, the rubber modifiedSTY/MMA/MAH copolymers of the present invention possess a uniquecombination of properties and are produced at a moderate cost. Therubber modified STY/MMA/MAH copolymers of the present invention,typically, possess a high degree of transparency (>80%), toughness(N.I.>3 ft.-lb/in) and heat distortion temperature (>95° C.).

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the present preferredembodiments of the invention.

The rubber-modified copolymers of the present invention can bepolymerized in any known reactor (e.g. autoclaves). However, a preferredmeans of polymerizing the copolymers of the present invention is a twinscrew extruder reactor. The operation of the twin screw extruder is setforth in detail in U.S. Pat. No. 4,463,137 herein incorporated byreference.

The rubber-modified copolymer of the present is prepared by polymerizingthe single nonaqueous emulsion feedstock of the present invention. Mostpreferably, the nonaqueous feedstock is substantially free of any inertorganic solvent. The feedstock comprises a nonaqueous emulsioncomprising rubber, a block copolymer having at least one componentmiscible with the rubber and at least one component miscible with themonomer and at least two miscible organic monomers, at least one of themonomers being a solvent for the rubber, and the mixture of the monomersbeing substantially a nonsolvent for the rubber. The rubber ismaintained (held) in emulsified form within the monomer mixture by theblock copolymer. Preferably, the organic monomers are unsaturated andcapable of free radical polymerization.

Most preferably, the feedstock comprises a nonaqueous emulsion of arubber, a monoalkenyl aromatic monomer, an unsaturated dicarboxylicanhydride, a C₁ to C₃ alkyl methacrylate and/or acrylonitrile and ablock copolymer having at least one component miscible with the monomerand at least one component miscible with the rubber. The function of theblock copolymer is to stabilize the nonaqueous emulsion feedstock in asimilar manner to that of a surfactant used in making aqueous emulsions.The block copolymer prevents or substantially delays the rubber phasefrom precipitating out during mixing of the monomers and rubbercomponent of the nonaqueous emulsion feedstock. This results in theformation of a stable emulsion suitable for direct polymerizationwithout the aid of any conventional solvent (e.g. methyl ethyl ketone).

In particular, the method of fabricating the feedstock of the presentinvention comprises (1) mixing at least a portion of the C₁ to C₃methacrylate, the monoalkenyl aromatic monomer, rubber and blockcopolymer in a first container to form a first nonaqueous solution, (2)mixing the remaining portion of a C₁ to C₃ alkyl methacrylate and theunsaturated dicarboxylic anhydride in a second container to form asecond nonaqueous solution, and combining the two solutions withstirring to produce the nonaqueous stable emulsion feedstock comprisingrubber or rubber-rich particles in the monomer mixture. In addition,further monomer can be added at this point without disturbing thestability of the feedstock but to enable one to change thecharacteristics of the resultant polymer. Such flexibility is highlydesirable as described in Examples VII and VIII below. Finally, the sizeof the rubber or rubber-rich particles present in the emulsion rangesfrom about 0.1 to 10 microns. This feedstock can be polymerized in areactor extruder apparatus as described in U.S. Pat. No. 4,463,137.

Preferably, the concentration of the components comprising thenonaqueous emulsion feedstock of the present invention are about 5 to 60(most preferably 15 to 50) pbw monoalkenyl aromatic monomer (e.g.styrene), about 25 to 80 pbw (most preferably 30-70) C₁ to C₃ alkylmethacrylate (e.g. methyl methacrylate), about 5 to 30 pbw (mostpreferably 10-25) dicarboxylic unsaturated anhydride (e.g. maleicanhydride) and 5 to 30 pbw (most preferably 10-20) block copolymer (e.g.styrene/butadiene) and rubber.

In a preferred embodiment of the present invention acrylonitrile issubstituted in part for the C₁ to C₃ alkyl methacrylate in the nonrubbercontaining solution.

The process of fabricating the rubber-modified thermoplastic copolymersof the present invention comprises preparing a stable nonaqueousfeedstock according to the procedure of the present invention, placingthe feedstock in a polymerization apparatus and heating the feedstock,optionally, in the presence of an initiator, to polymerize the monomersto form a rubber-modified thermoplastic copolymer possessing superiorrubber particle dispersion, increased heat distortion temperatures, andimproved impact strength.

Typically, the nonaqueous emulsion feedstock is fed into a reactorextruder and polymerized in the presence of an initiator (i.e. about0.03 to 0.3 weight %) such as benzoyl peroxide at an elevatedtemperature (e.g. 120° to 200° C.) for time sufficient to effectpolymerization (e.g. 2 to 20 minutes). It should be understood thatbenzoyl peroxide is merely illustrative of the types of initiators whichmay be utilized in the practice of the present invention. Any othersuitable organic peroxide initiator such as dicumyl peroxide may beutilized.

The preparation of two preliminary solutions seems to be an essentialstep in the process of this invention, in order to obtain the desiredemulsion of rubber or rubber-rich particles in the monomer mixture. Forexample, the rubber and block copolymer must be present in the samepreliminary solution or the rubber will not emulsify and will remain asa coagulated mass just as if the block copolymer were not present.Moreover, other optimum process details such as the order of addition ofthe two preliminary solutions to each other (usually the rubber freesolution should be added to the rubber solution) and the relative ratiosof the common third monomer in the preliminary solutions will vary asthe components vary, but will be readily determined by one skilled inthe art.

The following examples set forth below are illustrative of the preferredembodiments of the present invention.

EXAMPLE I

14.7 part Maleic Anhydride was dissolved into 19.7 parts methylmethacrylate (MMA) to form nonaqueous solution I. Next 15.6 partsstyrene was blended into 50.0 parts MMA and then 10.9 partspolybutadiene rubber (high cis 1,4 polybutadiene; Typical Mooney ML₁₊₄at 100° C.=25-35) and 10.9 parts styrene-butadiene block copolymer(linear diblock copolymer with Styrene/butadiene ratio 25/75 Molecularweight 83,000) were added to form nonaqueous solution II. Once bothsolutions I and II were fully dissolved, solution I was slowly added tosolution II over approximately 4 hours during which time both solutionswere continuously agitated. The resulting nonaqueous emulsion feedstockhad a dispersion of small rubber particles in a reactive monomersolution.

This feedstock was bulk polymerized in a reactor-extruder at atemperature of about 120°-180° C. using 0.11% benzoyl peroxide as aninitiator and 9 minute reaction time. The resulting polymer product hada 75% light transmission, a HDT of 83° C., and an impact strength of 3.3ft-lb/in notch.

EXAMPLE II

A feed was prepared in the manner described in Example I but with afinal composition of 70 parts methyl methacrylate, 15 parts MAH, 15parts styrene and 7.7 parts each of the block copolymer and rubber usedin Example I. This feed was polymerized as in Example I. Dicumylperoxide, (0.13%) was used as initiator. A reaction time of 5-6 minuteswas used. The polymer product properties were:

    ______________________________________                                        Reaction time        6 min.  5 min.                                           ______________________________________                                        Notched Izod (ft-lb/in notch)                                                                       3.1     2.7                                             HDT (°C.)     87.0    96.0                                             Light Transmission (%)                                                                             73.0    74.0                                             ______________________________________                                    

EXAMPLE III

A feed was prepared as in Example II, but polymerized using benzoylperoxide (0.15%) as initiator, with an 11 minute reaction time. Theproduct properties were as follows:

Notched Izod (ft-lb/in notch): 4.0

HDT (°C.): 81.0

Light Transmission (%): 70.0

EXAMPLE IV

A feed was prepared by the procedure of Example II. The feed wasmodified through the addition of 11 parts of a 1:1 (mole ratio) solutionof styrene and maleic anhydride to produce a feed of the followingcomposition (with reduced rubber content):

62 parts MMA, 19 parts of styrene, 19 parts of MAH, 6.9 parts blockcopolymer and 6.9 rubber (polybutadiene). This feed was polymerized at120°-180° C., using dicumyl peroxide initiator (0.12%), with a 7 minutereaction time. The polymer product had properties shown below.

Notched Izod (ft-lb/in notch): 1.6

HDT (°C.): 98.0

Light Transmission (%): 80.0

EXAMPLE V

Solution I was composed of 24.4 parts maleic anhydride (MAH) and 29.5parts Acrylonitrile (AN). Solution II was made of 5.4 parts rubber (cis1,4-polybutadiene), 5.4 parts styrene/butadiene diblock copolymer,(styrene 25%, butadiene 75%.), and 46.1 parts styrene. By stirring andmixing together the Solutions I and II, a stable emulsion solution wasformed. Upon examination of the solution under a phase contrastmicroscope, the rubber particle size is <1 micron. The solution waspolymerized in a test tube in the presence of 0.2% benzoyl peroxide at90°-100° C. for 20 minutes to give a uniform looking product.

EXAMPLE VI

Four batches of emulsified feed solutions were prepared in 5 gallonreactors. Each of these solutions involved blending an AN/MAH solution(I) to a styrene/rubber/block copolymer solution (II) in ten incrementsover 5 hours. The rubber and block copolymer in Solution II was a blendof 2 parts of a diblock copolymer containing 25% styrene and 75%butadiene to 1 part rubber (polybutadiene). The following table showsthe compositions of the A and B solutions:

    ______________________________________                                                 Solution I    Solution II                                            Solution #                                                                             (parts in feed)                                                                             (parts in feed)                                        ______________________________________                                        10496-79-S1                                                                            20.5 AN/27.0 MAH                                                                            52.5 S/25.8 rubber & block                                                    copolymer                                              10496-79-S2                                                                            20.6 AN/27.2 MAH                                                                            52.5 S/15.6 rubber & block                                                    copolymer                                              10496-79-S3                                                                            36.9 AN/16.5 MAH                                                                            46.5 S/22.9 rubber & block                                                    copolymer                                              10496-79-S4                                                                            27.1 AN/20.3 MAH                                                                            52.6 S/25.9 rubber & block                                                    copolymer                                              ______________________________________                                    

The emulsion feedstock was then polymerized by continuously pumpingthese solutions, together with a 5% benzoyl peroxide solution in adesired ratio, into a 28 mm twin screw reactor-extruder at temperaturesof 120°-190° C. (from Zone 1 to die), and with residence time of about 5minutes. The monomer conversions were 35-70%. The crude polymer productswere mechanically ground at room temperature and dried in an oven at100° C. for 2 hours. The dried products were compression molded intotest bars for physical property measurements. The following table showssome selected physical properties:

    ______________________________________                                                Notched          Break         Tensile                                        Izod     HDT     Strength                                                                             % Elong.                                                                             Modulus                                Solution #                                                                            (ft-lb/in)                                                                             (°C.)                                                                          (psi)  at break                                                                             (psi)                                  ______________________________________                                        10496-79-S1                                                                           3.1      131     4800    6.9   2.3 × 10.sup.5                   10496-79-S2                                                                           2.0      133     6500    2.8   3.4 × 10.sup.5                   10496-79-S                                                                            3.3      105     4500   14.0   2.0 × 10.sup.5                   10496-79-S4                                                                           3.4      122     4000   13.0   1.7 × 10.sup.5                   ______________________________________                                    

EXAMPLE VII

In this example acrylonitrile was substituted in part for the MMA.

Methylmethacrylate (MMA) was added to a nonaqueous emulsion of styrene(STY)/acrylonitrile (AN)/maleic anhydride (MAH)/polybutadienerubber/styrene-butadiene (S-B) block copolymer made by the procedure ofExample VI (solution #1496-79-S4) to form a nonaqueous stable emulsionthat was then polymerized in a reactor-extruder using 0.13% benzoylperoxide and a 6 minute reaction time. The net feed composition was 26.7parts MMA, 38.5 parts STY, 19.9 parts AN, 14.9 parts MAH, 6.3 partspolybutadiene rubber, and 12.6 parts S-B block copolymer.

The rubber-modified product of this example had an improved transparencyover opaque polymers which did not contain MMA. Transparency for thispolymer was 31%.

EXAMPLE VIII

The same procedure was followed as described in Example VII above.However, the net feed composition was 57.4 parts MMA, 22.4 parts STY,11.5 parts AN, 8.7 parts MAH, 3.7 parts polybutadiene rubber, and 7.3parts S-B block copolymer.

Transparency was approximately 36%.

EXAMPLE IX

The solutions were prepared and polymerized according to Example VI.

    ______________________________________                                        Solution I    AN = 42.7 parts                                                               MAH = 9.2 parts                                                 Solution II   Styrene = 48.1 parts                                                          EP Rubber                                                                     (ethylene 40% - propylene 60%)                                                Styrene/ethylene - propylene/                                                 styrene triblock copolymer                                                    (29% styrene)                                                   ______________________________________                                    

The physical properties of the resulting rubber modified thermoplasticpolymer were:

    ______________________________________                                         ##STR1##           0.6; 0.8                                                  HDT (unannealed)(°C.)                                                                      91; 92                                                    Break Strength (PSI)                                                                              5300; 5500                                                % Elong. at Break   1.6; 1.8                                                  Tensile Modulus (PSI)                                                                             3.5 × 10.sup.5 ; 3.8 × 10.sup.5               ______________________________________                                    

EXAMPLE X

In this example, methyl methacrylate (MMA) was substituted foracrylonitrile (AN) to produce a rubber-modified S/MMA/MAH terpolymer.The rubber and block copolymer in this case was a blend of 1 partdiblock copolymer (25% styrene-75% butadiene) to 1 part rubber(polybutadiene). The solutions used in this case are the following:

    __________________________________________________________________________          Solution I Solution II                                                  Solution #                                                                          (parts in feed)                                                                          (parts in feed)                                              __________________________________________________________________________    10496-98-2                                                                          19.7 MMA/14.7 MAH                                                                        15.6 S/50.0 MMA/22.0 Rubber and Block Copolymer              10496-98-3                                                                          12.9 MMA/19.3 MAH                                                                        51.1 S/16.7 MMA/22.1 Rubber and Block Copolymer              __________________________________________________________________________

These solutions were polymerized and processed in a similar manner toexample VIII. Results of physical testing were as follows:

    ______________________________________                                                 Notched          Break         Tensile                                        Izod     HDT     Strength                                                                             % Elong.                                                                             Modulus                               Solution #                                                                             (ft-lb/in)                                                                             (°C.)                                                                          (psi)  at break                                                                             (psi)                                 ______________________________________                                        10496-98-2                                                                             3.3       83     3800   58.0   1.4 × 10.sup.5                  10496-98-3                                                                             3.0      119     3300    9.9   1.8 × 10.sup.5                  ______________________________________                                    

As evidenced by the above examples, the rubber-modified terpolymers ofthe present invention comprising styrene, methyl methacrylate and maleicanhydride exhibit a high transparency >(80%), toughness (e.g. N.I.>3 ft.lb/in.) and heat resistance (HDT>95° C.). Rubber-modified copolymers ofthe present invention comprising styrene, maleic anhydride andacrylonitrile substitute in part or wholly for methyl methacrylatepossesses high impact strength, high heat distortion temperature andexcellent uniformity. The resulting rubber-modified copolymers of thepresent invention have a broad range of uses as evidence by U.S. Pat.Nos. 4,341,695 and 4,463,137. In particular, the rubber modifiedcopolymers of the present invention may be used as appliance housing andthe like.

The foregoing description of the preferred embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and obviously many modificationand variations are possible in light of the above disclosure. Theembodiments were chosen and described in order to explain best theprinciple of the invention and its practical applications to therebyenable others skilled in the art to best utilize the invention in itsvarious embodiments and with various modifications as are suited to theparticular were contemplated. It is intended that the invention bedefined by the claims appended hereto.

What is claimed is:
 1. A rubber-modified transparent thermoplasticcopolymer composition comprising a monoalkenyl aromatic monomer, anunsaturated dicarboxylic acid anhydride monomer, a C₁ to C₃ alkyl esterof methacrylic acid monomer, an acrylonitrile monomer, a rubber, and ablock copolymer having at least one component miscible with saidmonomers and at least one component miscible with said rubber, whereinsaid rubber modified copolymer is prepared by polymerizing a singlenonaqueous emulsion feedstock comprising each said monomer, said rubberand said block copolymer.
 2. The thermoplastic copolymer composition ofclaim 1 wherein said C₁ to C₃ alkyl ester of methacrylic acid and saidacrylonitrile are present in the range of about 50 to 80 parts byweight.
 3. The thermoplastic composition of claim 1 wherein said blockcopolymer is styrene/butadiene or styrene/ethylene-butylene.
 4. Thethermoplastic composition of claim 1 wherein said rubber is selectedfrom the group consisting of polybutadiene, ethylene/propylene andethylene/propylene/diene.
 5. The thermoplastic copolymer composition ofclaim 1 wherein said monoalkenyl aromatic monomer is selected from thegroup consisting of styrene and its derivatives.
 6. The thermoplasticcopolymer composition of claim 5 wherein monoalkenyl aromatic monomer isstyrene and said styrene is present in the range of about 5 to 30 partsby weight.
 7. The thermoplastic composition of claim 1 wherein saidunsaturated dicarboxylic acid anhydride is selected from the groupconsisting of maleic anhydride, itaconic anhydride, citraconicanhydride, and aconitic anhydride.
 8. The thermoplastic composition ofclaim 7 wherein said anhydride is present in the range of about 5 to 30parts per weight.
 9. The thermoplastic copolymer composition of claim 1wherein said C₁ to C₃ alkyl ester of methacrylic acid is selected fromthe group consisting of methyl methacrylate, ethyl methacrylate andpropyl methacrylate.
 10. The rubber-modified thermoplastic copolymercomposition of claim 1 wherein methacrylonitrile is substituted foracrylonitrile.
 11. The rubber modified thermoplastic copolymercomposition of claim 1 wherein said block copolymer is styrene/butadieneor styrene/ethylene-butylene.
 12. The rubber-modified thermoplasticpolymer composition of claim 1 wherein said block copolymer is astyrene/butadiene copolymer wherein at least about 25 weight parent ofsaid block copolymer comprises styrene.
 13. A rubber-modifiedthermoplastic polymer compositions of claim 1 wherein said rubber andsaid block copolymer are present in the range of about 5 to 25 parts byweight.